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New Heights on Old Foundations
The redevelopment of One Victoria, in London, England, is transforming the site of a former 1960s office block into a modern, sustainable and low-carbon workplace in the heart of Westminster. A key feature of the project is the retention of large parts of the existing structure and foundations. By avoiding the need for new piling, the project significantly reduces embodied carbon. For the tower crane concept, however, this approach created highly unusual conditions in central London: the WOLFF cranes had to be installed at basement level, on foundations more than 60 years old – which was far more challenging than it sounds. The crane concept for One Victoria Street is divided into several construction phases and includes a total of 9 WOLFF cranes. The project began with demolition works carried out by engineering firm Keltbray Group Limited. To support operations on the confined and complex site, a WOLFF 355 B luffing jib crane (TC0) was deployed. With its compact luffing jib design, the crane proved particularly well suited to the restricted site conditions. At the same time, its combination of reach, lifting capacity and precision was essential for safely positioning heavy and awkward loads. Throughout the demolition phase, the WOLFF 355 B handled all major heavy lifts, including excavators, tracked loaders, dumpers, heavy skips, generators and structural steel.
The installation sequence in the basement required meticulous coordination. As the demolition crane TC0 remained in service longer than anticipated, TC2 (WOLFF 355 B) was initially erected at a reduced height to prevent any potential clash. Once TC0 was dismantled, TC2 was climbed to its full working height of 50 m. One of the project’s greatest engineering challenges was the installation of the cranes on the original foundations of the existing building. As these foundations are being reused without re-piling, each crane had to be positioned directly over the available foundation support points and the crane configuration adapted to the building structure. The location of both the cranes and their support points was therefore dictated by the existing structural layout. As a result, neither the free positioning of the cranes nor the conventional practice of anchoring them into purpose-built concrete foundations, as is typical on new-build projects, was possible. To overcome this challenge, WOLFFKRAN deployed its WOLFF cross-frame system. The system allows each of the 4 support legs to be individually adjusted to different lengths ranging from 6 to 10 m. In addition, the entire crane tower was rotated to align precisely with the available support points within the original foundation structure.
As construction progresses, the basement slab will be cast around the crane bases, leaving only the tower openings accessible. One of the most demanding aspects of the project still lies ahead: dismantling the cranes within the basement structure. The basement slabs are being cast extremely close to the crane towers, meaning the cross-frame and ballast will eventually become almost fully enclosed by the building structure. In addition, only very limited headroom and working space will be available below ground. As dismantling using conventional mobile cranes will not be possible under these conditions, a combination of ceiling hoists, low-level forklifts and skating systems will be used to remove the central ballast blocks and cross-frame in a controlled and precise manner before transporting all crane components out of the building. Two WOLFF 355 B (TC 5,6) and 2 WOLFF 630 B (TC 7,8) luffing jib cranes will then take over lifting operations for the upper floors as well as the installation of the façade and building services. Once completed, One Victoria Street will provide modern office and retail space in the centre of Westminster while retaining around 52% of the original 1960s structure, significantly reducing the project’s embodied carbon. Occupation is planned for early 2028.
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Following demolition, the next construction phase began for Mace Construct. Four additional WOLFF tower cranes – one WOLFF 166 B (TC 1) and 3 WOLFF 355 B (TC 2,3,4) – were installed at B2 level to support the construction of the building core and early superstructure works. The cranes also supported the slipforming process used for the concrete core. In this method, the formwork continuously moves upwards while concrete is poured almost without interruption, placing high demands on timing, material flow and crane availability.
For TC2, the constraints were particularly demanding: four different leg lengths were required within a single cross-frame base to achieve the correct alignment with the available support points. This solution demonstrates how flexibly the WOLFF cross-frame system can adapt to highly irregular legacy structures.
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